1. Field of the Invention
The present invention relates to breather assemblies for electrical apparatus, and more particularly, to a breather assembly which permits venting to the atmosphere of the interior of a high voltage fuse to maintain equal pressure while precluding the admittance of moisture to the interior of the fuse.
2. Description of the Prior Art
High voltage fuses for interrupting current in high voltage circuits are well known in the art. For example, U.S. Pat. Nos. 3,267,235 - Barta, 3,575,683 - Fahnoe, 3,176,100 - Barta, and 3,855,563 - Cameron et al., illustrate typical fuses for high voltage electric power circuits. Such high voltage fuses are often mounted outside on utility poles, and thus are directly exposed to adverse weather conditions including rain, sleet, hail, and snow. Since such high voltage fuses usually comprise an arc quenching material such as boric acid or other such materials which if exposed to moisture will deteriorate thereby jeopardizing proper operation of the fuse, such high voltage fuses typically have been hermetically sealed to prevent the entrance of moisture to the interior thereof. Any sealing material used to seal such fuses must provide a moisture tight seal without degradation despite years of outdoor exposure.
Despite attempts to provide a reliable hermetically sealed fuse which will maintain its sealed relationship even after years of use, it has been discovered that rough handling, thermal expansion of various parts of the fuse formed from dissimilar materials, corrosion, and exposure to adverse weather conditions all contribute to cause small leaks to develop after a period of time despite the best attempts to totally and completely hermetically seal a fuse. Once even the smallest of leaks develops, a phenomenon called "pumping" results which causes the ingress of moisture into the interior of the fuse. Pumping results because of the well known physical relationship of pressure, volume, and temperature. Since the fuse has a constant interior volume, any change in the temperature of that volume correspondingly results in a change in the pressure in the interior of the fuse. Thus, when the temperature of the fuse drops rapidly, such as during a rainstorm, the interior pressure of the fuse tends to drop rapidly so that the interior pressure is less than the atmospheric pressure causing any moisture on the surface of the fuse to be sucked through any existing leaks around the various hermetic seals of the fuse. Once moisture is sucked into the fuse, it is retained in the fuse because there is no atmospheric venting to dry the interior of the fuse so that after a period of time there is a deterioration of the interior components of the fuse.
Accordingly, it has been discovered that it would be an advantageous advance in the art to provide a versatile, economical breather assembly for high voltage fuses which permits atmospheric venting to the interior of the fuse while precluding the admittance of moisture to the interior of the fuse regardless of the positional orientation of the fuse but which does not degrade the efficiency of the current interruption function of the fuse. The present invention is directed to such a breather assembly for a high voltage fuse and other electrical apparatus.
Breathers for switch operating mechanisms are known in the art as illustrated in U.S. Pat. No. 3,696,729 - Chabala, et al., but the fuse breather described and claimed herein is believed to be unique.